Third generation partnership project (3GPP) mobile communication systems based on a wideband code division multiple access (WCDMA) radio access technology are widely spread all over the world. High-speed downlink packet access (HSDPA) that can be defined as a first evolutionary stage of WCDMA provides 3GPP with a radio access technique that is highly competitive in the mid-term future. However, since requirements and expectations of users and service providers are continuously increased and developments of competing radio access techniques are continuously in progress, new technical evolutions in 3GPP are required to secure competitiveness in the future. Reduction of cost per bit, increase of service availability, flexible use of frequency bands, simple structure and open interface, proper power consumption of a mobile station, and the like are defined as requirements.
An orthogonal frequency division multiplexing (OFDM) system capable of reducing inter-symbol interference with a low complexity is taken into consideration as one of post-third generation wireless communication systems. In the OFDM, a serially input data symbol is converted into N parallel data symbols, and is then transmitted by being carried on each of separated N subcarriers. The subcarriers maintain orthogonality in a frequency dimension. Each orthogonal channel experiences mutually independent frequency selective fading, and an interval of a transmitted symbol is increased, thereby minimizing inter-symbol interference.
Meanwhile, in the wireless communication system, a base station (BS) or a mobile station (MS) transmits data, and the MS or the BS transmits acknowledgement (ACK)/non-acknowledgement (NACK) for the data upon receiving the data. When the ACK/NACK is transmitted after a specific time elapses from transmission of data, this is called synchronous ACK/NACK.
If the wireless communication system employs a relay station (RS), data and ACK/NACK can be transmitted via the RS. In this case, a problem arises in that the method for transmitting data and ACK/NACK in the conventional wireless communication system employing only the BS and the MS cannot be directly used in the wireless communication system employing the RS. Accordingly, there is a need for a method for transmitting data and ACK/NACK in the wireless communication system employing the RS.